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      06-26-2015, 10:26 PM   #1
loesch
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Drives: 2011 BMW 135i M Sport
Join Date: Feb 2012
Location: State College, PA

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DIY: Locating boost leaks in N55

First, I do not claim to be an expert by any means. This is just an account based on my experience.

So how did I come to the conclusion that I have a boost leak? The first thing that I noticed was that I was not hitting targets, especially at higher RPMs. I saw some other people with logs showing 17psi at 6,000rpms so I figured something wasn't right. Also, PWM spikes almost immediately to 99. This shouldn't happen at lower RPMs like this.


Newguy123 was a big help as he pointed me to the company that puts together a tester that works perfectly for the N55. http://turboboostleaktesters.com/n55-engine-all-models/. It's a very nicely put together tool. Just make sure they send 2 clamps with it. Mine first showed up with just the one so I couldn't attach it to the inlet tube. They were great about it and sent another one to me right away though.

This tester is a must for us. Pure has said that 90% of the cars they get in their shop have some sort of leak. That says it all.

Starting the test

First, Remove the under body plastics so you can get a friend to help find leaks while you have the system under pressure. This is super easy and just requires the removal of several bolts.

1, Unclip the intake from the airbox. If you have the stock intake then unclip the top part of the airbox. You might be able to get away with leaving it but I would just remove the clips to make things less prone to breaking.
2, Loosen the flat head screw on the worm clamp shown in the image below. Squeeze and pull the intake free
3, 4, Remove the 2 screws that hold in the EGR fitting. Carefully pull it straight up and out.
5, Remove the 10mm bolt that secures the intake tube.

Now remove the intake tube.


Now you have access to the mounting point for the boost leak tester shown below.


Remove the rubber gasket from the turbo inlet tube. In this instance I have the Pure inlet tube but it should be the same procedure for the stock inlet tube.


Pre-tighten the bottom clamp on the boost leak tester until it won't fall off. Align it as shown in the pictures below...




Now seat the tester onto the flange of the turbo inlet tube and tighten the clamp to secure it.


Get out your air compressor fill to about 25psi. You don't want too much because you want to add pressure to the system gradually. Attach the air hose. You will use a standard tire inflator tool. Now REMOVE THE OIL CAP!! This helps to let the crankcase pressure escape to save your seals. Slowly add air until the tester gauge reads about 3 - 5 psi. At this point you may already find your leak. You'll hear air hissing and can feel around and listen to see where it's coming from. As you fix your leak(s), keep increasing the pressure slowly until about 20psi on the tester. In my case the air was escaping from the hot side charge pipe at only about 4psi. I had thought it was goodentight but apparently not.


While I was in there I also decided to empty my catch can. Always a good idea to do that every once in a while. I had a good bit of watery grossness to dispose of.
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2011 135i M Sport 6MT LeMans Blue | Active Autowerke Gen II axle back | Berk d******* | N54 gutted mids | FuelIt Walbro 450 fuel pump | Pure Turbos Stage 2 | 3.5bar TMAP | Pure Turbos inlet pipe | BMS intake | BMS oil catch can | ETS intercooler | ETS charge pipe | BMS JB4 w/ ISO firmware | BMS backend flash stacked on PPK | Eibach springs | Whiteline rear subframe bushing inserts | cosmetic tidbits
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